1. Field of the Invention
This invention relates to a method of storing and shipping a blood serum reference composition as well as to a blood serum reference composition obtained thereby.
2. Description of the Prior Art
U.S. Pat. No. 3,876,375 (hereinafter referred to as Maurukas patent) is incorporated herein in toto by reference. The Maurukas patent discloses a stable, blood serum biological reference composition for use in analysis of biologically similar unknowns. Depending upon its precise constitution, the Maurukas composition has a freezing temperature at from about -20.degree. C. to about -30.degree. C. and is capable of extended storage in the liquid state. The Maurakas composition comprises, in its non-biological component, from about 60 to about 80 weight percent water and from about 20 to about 40 weight percent of at least one alkylene polyol having from 2 to 5 carbon atoms. The remainder of the composition is chiefly at least one natural biological material selected from a group consisting of blood serum, enzyme, metabolites, electrolytes, and hormones.
As noted in the Maurukas patent, the widely accepted procedure, prior to Maurukas' invention, was to preserve labile biologicals containing water by rapidly freezing them and storing them in the frozen state at low temperatures until ready for use. One problem pointed out by the Maurukas patent as being inherent in this prior art procedure is that freezing does, in some cases, produce insoluble turbidity when the biological material is brought back to the liquid state, and especially when it is brought to room temperature.
It is also well known to those skilled in the art that when serum is frozen to about -20.degree. C., there is some degradation of the proteins and enzymes and some loss of gases as they are squeezed out of the matrix during the freezing process. Repeated freezing and thawing of the serum will also dissociate isoenzymes of LDH and CPK. Therefore, when such serum is assayed for LDH and CPK isoenzymes, one obtains inaccurate values as to the relative percentage of each of these isoenzymes in the serum. The repeated freezing and thawing effect on serum proteins in general will cause a change in antigenicity with a decrease value for antigen-antibody reactions. This decrease in value for antigen-antibody reactions results in lower concentration values for the antigen being assayed.
To overcome the above problems inherent in freeze-drying serum as well as in storing serum at a temperature below the freezing point thereof, Maurukas removed from about 20 to about 40 weight percent water from frozen serum and added to the concentrated serum one or more alkylene polyols in an amount equal to the amount of water removed therefrom. Maurukas thereby obtained a biological composition which could be stored as a liquid at a temperature of from about -30.degree. C. to about room temperature.